1. Field of the Invention
The present invention relates generally to a medical device and procedures for employing the device. More particularly, it relates to a support catheter assembly with particular utility in facilitating insertion of a PTCA balloon into a lesion. The present invention also has utility as a stent, for maintaining a continuous passage, e.g., through an area of an artery or vein which is otherwise susceptible to collapsing or restenosing.
2. Description of the Prior Art
PTCA catheters and percutaneous medical procedures for angioplasty are well known. In such procedures, a flexible PTCA catheter generally is percutaneously inserted into a blood vessel of a patient and guided through the patient's vascular system to the location of a restriction. Insertion and manipulation of the PTCA catheter is frequently facilitated by use of a guide catheter. However, often these guide catheters are not able to reach all the way to the restriction. Thus, the gap between the distal end of the guide catheter and the stenotic region to be opened must be traversed by the PTCA catheter alone.
As those skilled in the art know, the distal end of a PTCA catheter is made to be extremely soft and flexible so as to facilitate its passage through tortuosities and restrictions in the vascular system. This flexibility, however, also makes the catheter readily susceptible to kinking and bending. The guide catheter is employed, at least in part, to restrict the radial deflection of the PTCA catheter and thereby prevent buckling and kinking.
The guide catheter, however, can generally reach only to the coronary ostia, whereas the lesion to be opened is most commonly located in one of the coronary arteries leading from the ostia. Thus, the balloon catheter must negotiate the ostia, enter the coronary artery and pass through the coronary artery to the lesion without the help of the guide catheter (see FIG. 14). The instant invention may be used to facilitate the passage of the balloon catheter from the end of the guide catheter to the lesion.
Support structures for advancing and guiding a PTCA balloon catheter are well known. As discussed above, a guide catheter provides an independent support structure. Integral support structures also have been developed. For example, U.S. Pat. No. 4,762,129 (Bonzel) describes a dilation catheter which includes a balloon capable of being enlarged by injecting a fluid through an aspiration tube that terminates in the balloon. The aspiration tube is arranged laterally offset from a segment of flexible tube that forms a passage through the balloon for a guide wire. The aspiration tube, which is reinforced with a stabilizing wire, also serves to transmit thrust and tension forces to push and pull the balloon to and fro and rotate it on the guide wire.
Coronary arterial stenoses generally are caused by the accumulation of plaque on the artery wall. Angioplasty reduces the arterial restriction by expanding a balloon within the stenotic region and compressing the plaque against the vessel wall, thereby increasing the size of the lumen in that region. However, the plaque has a tendency to return to its original form and again close down or severely restrict the arterial lumen. This restenosing, if it occurs, may occur as quickly as within only a few minutes, although it may not occur for a few weeks, or even for several months. The tendency for restenosis is of particular concern where angioplasty is performed preparatory to surgery, when it is imperative that the passage through the artery be kept open, at least until the surgeon has had an opportunity to operate.